1. Field of the Invention
The present invention relates to a spindle motor, an electronics device including the spindle motor, and a disk drive apparatus including the spindle motor.
2. Description of the Related Art
Spindle motors arranged to rotate disks are installed in hard disk drive apparatuses and optical disk drive apparatuses. Such spindle motors include a stationary portion fixed to a housing of the apparatus, and a rotating portion arranged to rotate while supporting the disk(s). While the spindle motor is running, a torque centered on a central axis is produced between the stationary portion and the rotating portion through interaction of magnetic flux. The rotating portion is thereby able to rotate with respect to the stationary portion.
A so-called fluid dynamic bearing is often used as a bearing of the spindle motor described above. The fluid dynamic bearing includes a stationary bearing portion, a rotatable bearing portion, and a lubricating fluid. A gap between the stationary bearing portion and the rotatable bearing portion is filled with the lubricating fluid. The rotating portion is supported by this fluid dynamic bearing to be rotatable with respect to the stationary portion.
The lubricating fluid in the fluid dynamic bearing described above gradually evaporates if the fluid dynamic bearing is used for a long period of time. A decrease in the amount of the lubricating fluid in the fluid dynamic bearing may lead to an inability of the rotatable bearing portion to rotate, or may cause the rotatable bearing portion to rotate while rubbing against the stationary bearing portion.
Accordingly, a structure of the fluid dynamic bearing which reduces evaporation of the lubricating fluid is required.